1. Field of the Invention
This invention relates to an audible signalling device for underwater use and, more particularly, to a manually actuated horn for underwater signalling between divers.
2. Description of the Prior Art
Much attention has been given to various acoustic signalling devices for use in air and underwater. One such effort is described in U.S. Pat. No. 259,782, entitled "Fog horn", which describes an air driven horn for use above water. A manually operated pump is used to force air through a vibrating reed assembly, which is connected to a trumpet in order to amplify the sound. Sound from air driven horns either ceases or is reduced to a low intensity when submerged in water, even though air is supplied to power the horns. Also, the sound from an air horn is reduced to a low buzz when submerged and powered by a stream of water.
Another effort is described in U.S. Pat. No. 929,623, entitled "Device for transmitting sound waves", which details a fluid driven horn for shipboard use. A vibrating diaphragm is built into the hull of a ship such that it is in contact with water on one side and with air on the other side. A pump forces air or water through a stationary nozzle onto the diaphragm. Periodic movement of the diaphragm allows the fluid to pass through a small opening between the nozzle and the diaphragm, causing it to emit sound into the water. This device requires that the diaphragm is in contact with air on one side and will not work if it is totally submerged in a body of water. A similar effort is described in U.S. Pat. No. 1,080,098, entitled "Submarine signalling", which teaches underwater signalling devices built around a valve that exhibits a "water hammer" effect. In this invention, water is forced under pressure through a nozzle with an extended surface area in contact with a resiliently supported stop plate. Hydraulic forces on the latter causes the rapidly streaming water to turn on and off, causing large variations in static water pressure. Sound is coupled into a surrounding body of water by combining this valve with a sound-radiating body, such as a metal pipe. Both water-powered underwater signalling devices require a high pressure pump for their operation, and are therefore not easily usable in diving.
Another effort is described in U.S. Pat. No. 3,125,061, entitled "Underwater fluid operated horn", which discloses a horn, driven by compressed air, for use underwater. This horn uses a sound-emitting diaphragm coupled to water on one side, and to a very small cavity supplied with compressed air on the other. The compressed air periodically forces the diaphragm to deflect, opening and closing an air passage between the diaphragm and a stationary sealing ring. The motion of the diaphragm couples sound waves to the water. The expended air is directed to one side of the horn, where the bubbles have the effect of absorbing some of the sound from the diaphragm.
U.S. Pat. No. 4,095,667, entitled "Portable underwater signalling transducer", describes another signalling device, which consists of a pneumatically driven jack-hammer that emits sound into a body of water as a result of the hammer striking a metal diaphragm.
Two very similar signalling devices are described in U.S. Pat. Nos. 4,852,510 and 4,893,580, both entitled "Scuba whistle", which consist of a pneumatically driven whistle, enclosed inside a resonant pipe. The whistle makes the pipe vibrate and the outside of the pipe, which is in contact with a body of water, transmits the sound.
A conventional air horn is described in U.S. Pat. No. 4,950,107, entitled "Audible alarm device for divers", for use by divers above water. Compressed air from a tank is forced through a conventional horn. This device does not work when submerged in water.
A similar air horn for divers is described in U.S. Pat. No. 4,998,499, entitled "Underwater pneumatic horn", which can be used by a diver both above and under water, after reconfiguration. The horn works in a conventional fashion above water. Compressed air from a tank is used to periodically deflect a diaphragm which is in fluid connection to a trumpet. The trumpet is furnished with a screw-on cover with a built-in check valve for underwater use. To use the horn underwater, the diver must attach the cover to the trumpet and purge the horn of water before it can be used. The range of the horn underwater is approximately 300 feet.
Another effort is described in U.S. Pat. No. 5,022,790, entitled "Audible signalling system for divers", which consists of a combination of two signalling devices for use by a diver above and under water. A conventional pneumatic horn is used to signal above water. For signalling underwater, compressed air is routed through an oscillatory valve mounted on a diver's air tank. Air passing through this valve causes the valve stem to vibrate, coupling sound to the surrounding water via the tank, which functions as a sounding board.
Most prior art signalling devices suitable for use underwater require compressed air for their operation. The compressed air is usually supplied from the diver's supply of breathing air, which may be in short supply. A recent study reveals that 40% of all diving accidents, and an even higher percent of fatalities, are caused by an out-of-air condition. Use of a compressed air driven signalling device during a dive consumes air which would otherwise be available to the diver for breathing. Also, the use of such a signalling device to alert a companion diver of an out-of-air situation may not be possible. It is therefore desirable to utilize an underwater signalling device that works independent of a diver's supply of breathing air.
U.S. Pat. No. 4,858,204, entitled "Underwater signalling device", describes a manually operated underwater signalling device. The main parts consist of a clapper which is held preloaded against a striking plate by means of a spring. The clapper, when lifted and released, hits the striking plate which is in acoustical contact with a diver's air tank. The air tank, which acts as a resonator, transmits the impact sound into the surrounding water, over a range of up to 50 feet. It is generally accepted that the direction of an underwater sound source can only be judged by finding out if the sound gets louder or quieter by moving closer or further away from the source. Short-duration impact sounds make this judgement difficult. Also, the signalling device must be mounted on an air tank which is carried on the diver's back. This makes it inconvenient for a diver to operate the device.
One objective of the present invention is to reveal a new class of manually operated underwater signalling devices that work independent of a diver's supply of breathing air.
Another objective is to provide water powered underwater signalling devices that will operate without adjustments at any depth.
A further objective of the present invention is to provide small, self-contained signalling devices that can produce signals of extended duration, which can be heard underwater over long distances.
A final objective of the present invention is to provide underwater signalling devices that can be used for transmission of simple predefined messages.